I blame myself for the poor wording, because I, actually, agree with you Of course, interaction with the characters is, probably, the most important part of PS:T gameplay. What I meant to say is that the variety of choices in party composition was non-existent until the latter stages of the game, so it didn't really feel like you were choosing companions, but rather that the game was doing it for you. Mind you, the player was limited not only by the number of choices, but by availability of those choices as well. The companions arrived at certain plot points and some of those happened very late in the game (Vhailor is, probably, the most striking example of that, but Ignus, Fall-from-Grace and Nordom also joined up with you only around mid-game stage).
Now, compare it to Baldur's Gate 2 (I know, I keep bringing it up again and again, but I do think it had a nearly perfect balance between variety of choices and characterization of companions). Aside from Imoen, there were only 2-3 companions that required any kind of significant questing to get them in the party. Basically, you could quickly assemble the team you wanted to spend the rest of the game with right after leaving Irenicus' dungeon. And you were doing it on your own terms, not because those were the only choices around. And before someone mentions "Adventurer's Hall" again - no, that's not a valid alternative, because I could base my choices on degree how I liked or disliked the characters, their backstories or writing, while In case of the AH I'm forced to limit my criteria to classes and stats.